6mht | pdb_00006mht

TERNARY STRUCTURE OF HHAI METHYLTRANSFERASE WITH ADOHCY AND DNA CONTAINING 4'-THIO-2'DEOXYCYTIDINE AT THE TARGET

spinqualitylabelsall models 6mht, resolution 2.05Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6mht is a 3 chain structure with sequence from Haemophilus haemolyticus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: SAM NonStd Res: 4SC, 5CM Activity: Deleted entry, with EC number 2.1.1.73 Resources: FirstGlance, OCA, RCSB, PDBsum Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed 4'-Thio-2'-deoxycytidine was synthesized as a 5'- protected phosphoramidite compatible with solid phase DNA synthesis. When incorporated as the target cytosine (C*) in the GC*GC recognition sequence for the DNA methyltransferase M. HhaI, methyl transfer was strongly inhibited. In contrast, these same oligonucleotides were normal substrates for the cognate restriction endonuclease R. HhaI and its isoschizomer R. Hin P1I. M. HhaI was able to bind both 4'-thio-modified DNA and unmodified DNA to equivalent extents under equilibrium conditions. However, the presence of 4'-thio-2'-deoxycytidine decreased the half-life of the complex by >10-fold. The crystal structure of a ternary complex of M. HhaI, AdoMet and DNA containing 4'-thio-2'-deoxycytidine was solved at 2.05 A resolution with a crystallographic R-factor of 0.186 and R-free of 0.231. The structure is not grossly different from previously solved ternary complexes containing M. HhaI, DNA and AdoHcy. The difference electron density suggests partial methylation at C5 of the flipped target 4'-thio-2'-deoxycytidine. The inhibitory effect of the 4'sulfur atom on enzymatic activity may be traced to perturbation of a step in the methylation reaction after DNA binding but prior to methyl transfer. This inhibitory effect can be partially overcome after a considerably long time in the crystal environment where the packing prevents complex dissociation and the target is accurately positioned within the active site. DNA containing 4'-thio-2'-deoxycytidine inhibits methylation by HhaI methyltransferase.,Kumar S, Horton JR, Jones GD, Walker RT, Roberts RJ, Cheng X Nucleic Acids Res. 1997 Jul 15;25(14):2773-83. PMID:9207024 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also HhaI DNA methyltransferase

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